1. Field of the Invention
The present invention relates generally to a data recording apparatus and method, and more particularly, to a data recording apparatus provided in a computer system and a computer application equipment for recording continuous data such as images and voices and a data recording method carried out in the data recording apparatus.
2 Description of the Background Art
In recent years, in a PC (Personal Computer) and a home AV (Audio Visual) equipment, AV data digitized has been rapidly utilized through package media such as a CD-ROM (Computer Disk Read Only Memory) and a DVD-ROM (Digital Versatile Disk Read Only Memory)-ROM or communication media such as an internet and digital satellite broadcasting.
On the other hand, demands for recording of digital AV data by the PC and the home AV equipment have increased as a large-capacity hard disk unit or a rewritable optical disk unit which is detachably contained in a cartridge of an magneto-optical disk, a phase transition type optical disk, or the like has spread and a DVC-RAM (Random Access Memory) has appeared on the stage.
A moving image compression technique of an MPEG (Moving Picture Expert Group) system which is superior in the image quality and the compression rate has been mainly used today for digital AV data. For example, MPEG-2 which is close to broadcasting quality has been utilized as AV data for DVD which has been on the main current of a video disk. The data rate of the MPEG-2 is 3 to 11 Mbps (megabits per second). In an authoring apparatus for generating AV data for DVD-ROM, for example, however, a disk unit with a high speed which significantly exceeds 11 Mbps and a high-cost storage device such as a RAID (Redundant Array Inexpensive Disks) have been employed in order to record data with a rate of 3 to 11 Mbps. The reason for this is that digital AV data is continuous data over a long time period. In order to record the data in real time without interruption, therefore, fluctuations in the processing performance of a computer system constituting the authoring apparatus and the recording performance of the recording apparatus itself also be considered.
When an attempt to record the digital AV data by the PC is made, the recording speed is too low in the optical disk unit. In a standard hard disk unit, the recording speed thereof is higher than that of the optical disk unit but is not sufficient. In addition, the capacity thereof is insufficient. Although a hard disk unit for PC which is relatively low in cost has increased in speed year after year as the capacity thereof has increased, it is very difficult to record the digital AV data with a rate which is approximately equal to the rate of the MPEG-2 over a long time period.
Furthermore, in recording the digital AV data in a PC based system, continuous recording of data may, in some cases, be prevented by the following factors:
(1) overhead resulting from access to a file system depending on a relatively small allocation size, PA1 (2) operations peculiar to the recording apparatus, for example, access to a management data area, occurrence of seek by non-continuity of data areas, restart of a disk unit by a seek error, a temperature compensation operation, a write retry operation, and bad sector alternate processing, and PA1 (3) fluctuations in time of a processing operation by software sequential processing on a CPU (Central Processing Unit). PA1 first storing means for storing the data; PA1 second storing means in a parallel relation with the first storing means for recording a part of the data; and recording managing means for issuing a recording instruction to the first storing means and a recording instruction to the second storing means while mutually switching the recording instructions in accordance with a proceeding of the data feed. PA1 recorded state monitoring means for monitoring a state where the recording instruction to the first storing means issued by the recording managing means is executed, PA1 wherein the recording managing means determining which of the recording instruction to the first storing means and the recording instruction to the second storing means should be issued on the basis of the result of the monitoring by the recorded state monitoring means when the recording instruction to the first storing means and the recording instruction to the second storing means are issued while being mutually switched. PA1 the recorded state monitoring means comprises; PA1 the recording managing means judges whether or not the result of the measurement by the buffer data amount measuring means is not more than a first reference value, to issue the recording instruction to the first storing means when the result of the judgment is affirmative, while issuing the recording instruction to the second storing means when it is negative. PA1 issuing a recording instruction to the first storing means and a recording instruction to the second storing means while mutually switching the recording instructions in accordance with a proceeding of the data feed; and PA1 recording on the second recording means a part of the data to be recorded on the first storing means. PA1 monitoring a state where the recording instruction to the first storing means is executed: and PA1 determining which of the recording instruction to the first storing means and the recording instruction to the second storing means should be issued on the basis of the result of the monitoring when the recording instruction to the first storing means and the recording instruction to the second storing means are issued while being switched. PA1 in monitoring a state where the recording instruction to the first storing means is executed, PA1 in determining which of the recording instruction to the first storing means and the recording instruction to the second storing means should be issued, PA1 the step of judging whether or not the result of the measurement is not more than a first reference value; and PA1 the step of issuing the recording instruction to the first storing means when the result of the judgment is affirmative, while issuing the recording instruction to the second storing means when it is negative. PA1 in issuing the recording instruction to the second storing means, PA1 monitoring a state where the recording instruction to the first storing means is executed; and PA1 determining which of the recording instruction to the first storing means and the recording instruction to the second storing means should be issued on the basis of the result of the monitoring when the recording instruction to the first storing means and the recording instruction to the second storing means are issued while being mutually switched. PA1 issuing a transfer instruction to transfer data recorded on the second storing means toward the first storing means on the basis of the result of the monitoring. PA1 in mounting a state where the recording instruction to the first storing means is executed, PA1 in determining which of the recording instruction to the first storing means and the recording instruction to the second storing means should be issued, PA1 in issuing the recording instruction to the second storing means,
Therefore, the rate of the digital AV data which can be handled by the system is limited to not more than a value obtained by further subtracting a suitable margin from the worst value of the recording performance found in consideration of the above-mentioned preventing factors.
The apparent recording speed of the recording apparatus (as viewed from the CPU) has been conventionally increased not only for making the digital AV data recordable by the PC. One example is a method of providing a buffer memory in the storage device. A recent hard disk or optical disk has been generally equipped with a buffer memory having a capacity of 128 kilobytes to 2 megabytes. In this case, the effect of reducing the number of times of overhead described in the foregoing item (1) is also obtained by separating a recording request from the CPU and recording processing on the recording apparatus from each other and processing a plurality of recording requests from the CPU upon being collected as one recording request if possible.
However, in the above-mentioned buffer memory having a relatively small capacity, when the digital AV data is recorded, a buffer overflow sometimes occurs. Once the buffer memory is full of data, it goes without saying that the effect of increasing the apparent recording speed is not obtained.
In order to record the digital AV data by the PC, an auxiliary storage device with a speed higher than that of a storage device to be a target of writing (hereinafter referred to as a target storage device) has been conventionally provided at a front end of the recording apparatus, and used as a buffer or a cache. Typically, in recording the digital AV data on the optical disk by the PC, a method of creating an intermediate file as a buffer on the hard disk, to once store recording data from the CPU in the hard disk, and copy the stored data on the optical disk from the hard disk by background processing has been used.
A large-capacity and high-speed recording apparatus is realized by combining a high-speed auxiliary storage device with a target storage device having a large storage capacity and using the auxiliary storage device as a buffer device. Since the apparent recording speed is the recording speed itself of the auxiliary storage device, however, a storage device with a speed sufficiently higher than the rate of data to be recorded is still required. In the above-mentioned typical example, when an attempt to record the digital AV data on the optical disk by the PC, it is necessary to provide a hard disk unit with a speed sufficiently higher than the rate of the data.
In recording data, the amount of processing by the CPU is approximately three times, for example, data transfer to the auxiliary storage device, data reading from the auxiliary storage device, and data writing to the target storage device, as compared with that in a case where data is directly written into the target storage device.